1. Field of the Invention
The present invention relates to a trench embedding method and a film-forming apparatus.
2. Description of the Related Art
Semiconductor integrated circuit devices have a minute trench structure therein. A typical example of the minute trench structure is a STI (shallow trench isolation). An STI is a device isolation area for dividing active areas of a semiconductor device, and is formed by forming a minute trench on a silicon substrate and embedding an insulating material into the minute trench.
For example, an SOD (spin-on dielectric), as disclosed in Patent Reference 1, is known as an embedded insulating material. In particular, an inorganic polymer mainly including PHPS (perhydropolysilazane: SiH2NH) has attracted attention. When PHPS is fired in a vapor atmosphere, PHPS is changed into silicon oxide (SiO2). A reaction formula thereof is as follows.SiH2NH+2H2O→SiO2+NH3+2H2 
However, PHPS contracts when changed into silicon oxide. Thus, a gap is generated on a minute trench on which PHPS is changed into silicon oxide.
Accordingly, in Patent Reference 1, an expandable film is formed on a minute trench and then PHPS is embedded into the minute trench in prediction of contraction of PHPS. Such an expandable film may be a silicon (Si) film. In Patent Reference 1, a silicon film is expanded by being changed into a silicon oxide film, and thus contraction of PHPS is offset, thereby preventing a gap from being generated on a minute trench.
3. Prior Art Reference    (Patent Reference 1) U.S. Pat. No. 7,112,513